The stereochemistry of phosphoryl group transfer in both enzyme-catalyzed and un-catalyzed systems will be pursued. These experiments will focus on the mechanism of the actual phosphoryl transfer step in enzyme-catalyzed processes, and on the mechanistic details of uncatalyzed alcoholysis of phosphate monoesters in solution. Our studies on structural mutants of the plasmid-encoded Beta-lactamase from E. coli will be continued. This study aims to delineate the catalytic function of individual amino acid residues in Beta-lactamase, and link such changes to both the structure and function of this protein The inactivation of Beta-lactamases by 'suicide' reagents based on new modifications of the penam nucleus will be studied. This work will not only provide mechanistic information on Beta-lactamases, but also provide leads for the development of new reagents that can extend the range of effectiveness of existing Beta-lactam antibiotics.